The present invention relates to a shoe that is easily constructed and provides greater comfort to the wearer without affecting the fit or style of the shoe.
In order to understand the prior art and the present invention, it is necessary to understand the anatomy of the foot and the basics of shoe construction. FIG. 1 is a diagrammatic medial side view of the bones of the human foot 10, FIG. 1A is a rearward or heel-end view of the bones of the human foot, and FIG. 1B is a top plan view of the bones of the human foot. For purposes of this application, references to heelward or rearward mean in the direction of the rear of the foot or heel 20; references to forward or toeward mean in the direction of the front of the foot 30 where the toes or phalanges 31 are located; references to medial mean the side of the foot where the arch 40 is located; references to lateral mean the outside of the foot; and references to upper or top and lower, bottom or under assume the foot or shoe is oriented in an upright position.
The heel 20 of the foot (also known as the tarsus) includes the talus 21 and the calcaneus 22 bones. The rear lower surface of the calcaneus 22 has a slight protuberance 23 known as the calcaneal tuberosity.
Referring to FIG. 1A, the calcaneus is an irregularly shaped quadrangular bone also called the heel bone or os calcis. As can be seen particularly in FIG. 1A, the medial side of the calcaneal tuberosity, i.e. the lower part of the posterior surface of the calcaneus is not precisely on the same ground or plane as the lateral tuberosity. This slight difference in calcaneal anatomy leads to potential for instability on level surfaces, such as sidewalks, gym floors, hardwood, etc.
Referring also to FIG. 1B, the bones of the foot also include the navicular 41, the cuneiform 42, the metatarsals 45A-45E and the phalanges, or toes 31A-31E, with the big toe 31A visible in FIG. 1. The metatarsal heads 46A-46F are located at the forward end of the metatarsal shafts 47A-47E. Although it's one of the smaller parts of the body, all told the foot contains 26 bones, 33 joints and more than 100 muscles. Together, a person's two feet contain more than a quarter of all the bones in the human body which interact and undergo significant stresses during standing, walking and running.
Human footwear is designed to protect the human foot. However, as currently designed, human footwear is imperfect in providing proper biomechanical support for the human foot.
Also depicted in FIG. 1C is a partial cross-sectional view of the portions of a conventional shoe 50 that underlie the sole of the foot, the top parts of the shoe being shown in phantom. Shoe 50 has a heel 51 which is attached to the lower surface of sole 52 of shoe 50, with the sole 52 in turn supporting an insole board 53 on which a sock liner 54 is placed. In a conventional shoe, the insole board typically is of relatively rigid construction from the region underlying the wearer's heel to the heads of the metatarsals. Sock liners are commonly very flexible and generally are very thin, typically no more than half a millimeter thick. The sock liner is the surface upon which the sole of the foot normally rests.
In prior U.S. Pat. No. 4,597,195 to Dananberg (the '195 patent), there is described a human shoe sole having an area of reduced support underlying substantially only the location of the first metatarsal head of the wearer's foot. As described in the '195 patent, providing an area of reduced support substantially only under the head of the first metatarsal encourages eversion and plantar flexion of the first metatarsal head as weight shifts from the heel to the first ray. Thus, normal functioning of the foot for plantar flexion and supination is encouraged with beneficial results for improved walking comfort and shock absorption on subsequent heel contact. Prior PCT application WO 2011/017174 A1 describes an improvement in a human shoe sole or insole in which a depression provided underlying the first metatarsal head in which the depression has its lowest point skewed to the medial side of center. Millions of pairs of shoes have been manufactured and sold incorporating relief under the first metatarsal head as described above.